Brain Teaser

February 8, 2019

Less than 1 min to read

802

Dr. Johnson was walking in a park and met a family consisting of a grandfather, a father and a son. Dr. Johnson asked them how old they were. The grandfather said: “All together we are 100 years old”. The father said: “My son and I together are 45 years old, and my son is 25 years younger than I am”. How old are they?

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Answer: 55, 35, and 10

Let X1=age of the grandfather, X2 = age of the father, and X3 = age of the son. Then we have that:
X1+X2+X3=100
X2+X3=45
X2-X3=25
Solving this system of three equations, we get X1= 55, X2= 35, and X3=10